# Thread: field of view clarification

1. ## field of view clarification

I'm just a bit confused about this. The numbers in my example question are for the purposes of posing the question.

If I have two EP's with an effective magnification of 50, for example, and one has a field of view of 60, and the second has a field of view of 80, are the images actually the same, but the wider field EP just spreads it out more? OR, is the field of view of the 80 actually letting me see a larger area of the sky?

2. ## Re: field of view clarification

the images should be the same being each 50X- the second answer is correct, youll see a larger area of the sky

3. ## Re: field of view clarification

Originally Posted by spit
the images should be the same being each 50X- the second answer is correct, youll see a larger area of the sky
If the image is the 'same', then I should see the same area of the sky: one covers 60 degrees of view , the other the same image spread out over 80 degrees. This is why I'm confused!

How about this: Saturn looks the same in each of my EP in the example. But you are saying that the 80 degree EP will give me an actual larger area of sky around Saturn, so I would, perhaps, see more of the moons and or stars around Saturn.

4. ## Re: field of view clarification

by your original question, the word same was used in using 50X for each image- a wider FOV EP will show more area of the sky- but the 'spacing' as you put it, would be same at 50X with either EP- maybe someone has a link to a FOV calulator, i know they used to have them on the web, i dont have any links myself

5. ## Re: field of view clarification

50x is 50x, the image will be the same size with more space around it. Or if its a large object you see more of the object.
Clear Skies

6. ## Re: field of view clarification

Just picture looking through a paper tube 50mm wide and then through one 60mm wide, both looking at the same object in the center. The picture in the center is exactly the same with more revealed around the edges.

7. ## The Following User Says Thank You to davincisbeard For This Useful Post:

isoc (07-08-2013)

8. ## Re: field of view clarification

The answer depends on what you mean by "same".

The 60dFoV EP will have a true field of 1.2 degrees
The 80dFoV EP will have a true field of 1.6 degrees
Both fields are presented at the same scale (magnification)
But the eye is ever so willing to see the 80dFOV at lower magnificaiton simply because the field is bigger.

9. ## Re: field of view clarification

Heres a quick picture in paint (not to scale!) to show the point others are trying to make. Your target object will be the same size, but you will be seeing more of the area around it.

preview.jpg

10. ## The Following User Says Thank You to Intheflesh For This Useful Post:

isoc (07-08-2013)

11. ## Re: field of view clarification

As a remarkably intelligent person and an outstanding educator I wish to advise you that your dilemma is rooted in the way that you consider optical magnification to function.

Please toss out the traditional concept of linear magnification and replace it with the proper notion of angular magnification.

That object which is in the foreground is magnified by the same amount as the Deep Space behind it. The apparent magnification or increase in size is then dependent on the distance of the object or the Deep Space background from the telescope.

Problem solved? Feel free to thank me later. Buy me something small....like a farm, maybe!

12. ## Re: field of view clarification

Just checked...you can still get an ant farm by mail or post.

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